Electrodeposition process using partially esterified oil-acid adducts



United States Patent Ofiice 3,359,983 Patented Feb. 20, 1968 3,369,983ELECTRODEPOSITION PROCESS USING PARTIAL- LY ESTERIFIED OIL-ACID ADDUCTSDonald P. Hart, Allison Park, and Joseph E. Plasynski,

Arnold, Pa., assignors to Pittsburgh Plate Glass 60mpany, Pittsburgh,Pa., a corporation of Pennsylvania N Drawing. Filed May 24, 1963, Ser.No. 282,880 8 Claims. (Cl. 204-181) This invention relates to improvedcoating compositions adapted for use in electrodepositing films thereofon metals, and to the methods whereby such compositions are produced andelectrodeposited.

Electrodeposition of certain materials, and the methods used forelectrodepositing coatings have been known for some time. However, thetypes of materials heretofore used in electrodeposition processes havebeen necessarily limited because most of the compositions whichordinarily form desirable films and coatings cannot be satisfactorilyapplied in this manner, and the processes used to electrodeposit suchcompositions have been attended by serious disadvantages, such as poorflow of the deposited film and low throwing power. By throwing power ismeant that property whereby different areas of the electrode to becoated receive substantially the same density of deposit, even thoughthey are at appreciably different distances from the other electrode.

It has recently been discovered that certain specific coatingcompositions posses very desirable properties when used inelectrodeposition processes, and that the coatings electrodepositedtherefrom have excellent properties and can be applied easily andefficiently on a large scale. These coating compositions include thosein which the vehicle comprises the partially neutralized reactionproduct of a drying oil fatty acid ester or a semi-drying oil fatty acidester with an alpha, beta-ethylenically unsaturated dicarboxylic acid oran anhydride of such an acid. The compositions may also comprise thereaction product of the ester, acid or anhydride, and one or more otherethylenically unsaturated monomers. Many of these compositions aredisclosed in copending application Serial No. 222,674, filed Sept. 10,1962.

It has now been further discovered that a partially esterified reactionproduct of a fatty acid ester, an acid or anhydride, and optionally oneor more other monomers, provides coating compositions having greatlyimproved propertieswhen employed in electrodeposition processes. Thepartial esterification is carried out by reaction of the acidiccomponent with a monohydric alcohol at any stage of the process prior toneutralization of all or part of the remaining acidic groups.

Among the advantages of the improved coating compositions of thisinvention is the obtention of better flow properties on baking, aproblem often encountered in electrodeposition of coatings because ofthe high solids content of the film as deposited. In addition, it hasbeen found that harder coatings are achieved with these new coatingcompositions, a quite unexpected improvement in view of the better flowwhich is also obtained. Other significant advantages include an abilityto build heavier films during electrodeposition, improved throwing powerduring electrodeposition, and lower viscosity compositions, therebyproviding ease of formulation and increased salt-spray resistance of thefinal coating.

The foregoing advantages are particularly important with respect toelectrodeposited coatings. For this reason, and because the suitabilityof coating compositions for electrodeposition is both unpredictable anddiflicult to achieve, emphasis is placed herein upon the applicabilityof the compositions of this invention to electrodeposition processes.However, it should be noted that'these compositions can also be appliedby any conventional means, such as by brushing or rolling. Because theyare waterdispersible, their application by dipping and their use,

for example, as a dip primer, is advantageous in many instances, givingincreased salt-spray resistance and other improved properties. Thus, itis not intended that the invention be limited by the discussion andexamples herein relating to electrodeposition, although the usefulnessof these compositions in such processes makes them especially valuable.

The improved compositions of the present invention comprise a modifiedreaction product or adduct of the drying oil or semi-drying oil fattyacid ester with a dicarboxylic acid or anhydride. By drying oil orsemi-drying oil fatty acid esters are meant esters of fatty acids whichare or can be derived from drying oils or semi-drying oils, or from suchsources as tall oil. Such fatty acids are characterized by containing atleast a portion of polyunsaturated fatty acids. Preferably, the dryingoil or semi-drying oil per se is employed. Generally, drying oils arethose oils which have an iodine value of about 130, and the semi-dryingoils are those which have an iodine value of about to 130, as determinedby method ASTMD1467-57T. Examples of such esters include linseed oil,soya oil, safflower oil, perilla oil, tung oil, oiticica oil, poppyseedoil, sunflower oil, tall oil esters, walnut oil, dehydrated castor oil,herring oil, menhaden oil, sardine oil and the like.

Also included among such esters are those in which the esters themselvesare modified with other acids, including saturated, unsaturated oraromatic acids, such as butyric acid, stearic acid, linoleic acid,phthalic acid, isophthalic acid, terephthalic acid or benzoic acid, oran anhydride of such an acid. One inexpensive acid material which hasbeen found to produce good results in many instances is rosin, which iscomposed of chiefly abietic acid and other resin acids.

The acid modified esters are made by transesterification of the ester,as by forming a dior monoglyceride by alcoholysis, followed byesterification with the acid; they may also be obtained by reacting oilacids with a polyol and reacting the acid with the partial ester. Inaddition to glycerol, alcoholysis can be carried out using otherpolyols, such as trimethylolethane, trimethylolpropane, pentaerythritol,sorbitol and the like. If desired, the esters can also be modified withmonomers such as cyclopentadiene or styrene, and the modified estersproduced thereby can be utilized herein. Similarly, other esters ofunsaturated fatty acids, for example, those prepared by theesterification of tall oil fatty acids with polyols, are also useful.

Also included within the terms drying oil fatty acid esters andsemi-drying oil faty acid esters as set forth herein are alkyd resinsprepared utilizing semi-drying or drying oils; esters of epoxides withsuch fatty acids, including esters of diglycidyl ethers of polyhydriccompounds as well as other mono-, diand polyepoxides; semi-drying ordrying oil fatty acid esters of polyols, such as butanediol,trimethylolethane, trimethylolpropane, trimethylolhexane,pentaerythritol and the like; and semidrying or drying fatty acid estersof resinous polyols, such as homopolymers or copolymers of unsaturatedaliphatic alcohols, e.g., allyl alcohol or methallyl alcohol, includingcopolymers of such alcohols with styrene or other et'hylenicallyunsaturated monomers or with nonoil modified alkyd resins containingfree hydroxyl groups.

Any alpha, beta-ethylenically unsaturated dicarboxylic acid or anhydridecan be employed to produce the products described herein. These includesuch anhydrides as maleic anhydride, itaconic anhydride and othersimilar anhydrides. Insteadof the anhydride, there may also be usedethylenically unsaturated dicarboxylic acids which form anhydrides, forexample, maleic acid or itaconic acid. These acids appear to function byfirst forming the anhydride. Fumaric acid may also be utilized, althoughin many instances it requires more stringent conditions than theunsaturated dicarboxylic acid anhydrides or acids which form anhydrides.Mixtures of any of the above acids or anhydrides may also be utilized.Generally speaking, the anhydride or acid employed contains from 4 to 12carbon atoms, although longer chain compounds can be used if so desired.

While the exact nature of the reaction produce of the acid or anhydridewith the fatty acid ester is not known with certainty, it is believedthat the reaction takes place by addition of the unsaturated linkage ofthe acid or anhydride to the carbon chain of the oil. In the case ofnonconjugated double bonds such as are present in linseed oil, thereaction may take place with the methylene group adjacent thenonconjugated double bond. In the case of oils having conjugated doublebonds, such as tung oil, the reaction is probably of the Diels-Aldertype.

The reaction between the acid or acid anhydride and the drying oil orsemi-drying oil fatty acid ester takes place readily without the use ofa catalyst and at temperatures in the range of about 100 C. to about 300C. or higher, with the reaction generally being carried out betweenabout 200 C. and about 250 C.

While the reaction products can be comprised solely of adducts of thefatty acid ester and the dicarboxylic acid or anhydride, in manyinstances it is desirable to incorporate into the reaction productanother ethylenically unsaturated monomer. The use of such monomer oftenproduces films and coatings which are harder and more resistant toabrasion, and which may have other similar desirable characteristics.For this purpose, any ethylenically unsaturated monomer, preferablycontaining a single CH =C group, can be employed. Examples of suchmonomers include monoolefinic and diolefinic hydrocarbons, such asstyrene, alpha-methyl styrene, alpha-butyl styrene, vinyl toluene,butadiene-1,3, isoprene and the like; halogenated monoolefinic anddiolefinic hydrocarbons, such as alpha-chlorostyrene,alpha-bromostyrene, chlorobutadiene and similar compounds; esters oforganic and inorganic acids, such as vinyl acetate, vinyl propionate,vinyl 2-chlorobenzoate, methyl acrylate, ethyl methacrylate, butylmethacrylate, heptyl acrylate, decyl methacrylate, methyl crotonate,isopropenyl acetate, vinyl alpha-bromo-propionate, vinylalpha-chlorovalerate, allyl chloride, allyl cyanide, allyl bromide,allyl acetate, dimethyl itaconate, dibutyl itaconate, ethylalpha-chloroacrylate, isopropyl alpha-bromoacrylate, decylalphachloroacrylate, dirnethyl maleate, diethyl maleate, dimethylfumarate, diethyl fumarate and diethyl gultaconate; organic nitriles,such as acrylonitrile, methacrylonitrile and ethyacrylonitrile; and thelike.

As is apparent from the above discussion and the examples set forth,which, of course, do not include all of the ethylenically unsaturatedmonomers which may be employed, any such monomer can be utilized. Thepreferred class of monomers used can be described by the formula:

where R and R are hydrogen or alkyl, R, is hydrogen alkyl orcarboxyalkyl, and R is cyano, aryl, alkyl, alkenyl, aralkyl, alkaryl,alkoxycarbonyl or aryloxycarbonyl. The preferred compounds are styrene,substituted styrenes, alkyl acrylates, alkyl methacrylates, diolefinsand acrylonitrile.

The reaction of the fatty acid ester, the acid or anhydride, and anyadditional unsaturated monomer or monomers can be carried outconcurrently, that is, with each of the components of the reactionproduct being mixed together and heated to reaction temperature, or thefatty acid ester can be reacted first with monomer and then with theacidic component. However, because the monomer and the acid or anhydrideare often quite reactive with each other, the oil or other fatty acidester is in most instances preferably first reacted with the acid oracid anhydride, and then this product is subsequently reacted with anyethylenically unsaturated monomer or monomers employed. For example, areaction product of linseed oil, maleic anhydride and styrene isordinarily prepared by first reacting maleic anhydride with linseed oil,and then reacting the maleinized oil with styrene. When the process iscarried out in this manner, the reaction of the additional monomer withthe initial reaction product is usually carried out at somewhat lowertemperatures, usually between about 25 C. and 200 C.

The proportions of each of the components going to make up the reactionproduct are ordinarily not critical. Generally speaking, between about10 percent and about 45 percent by weight of the unsaturated acid oracid anhydride in reacted with from about 55 percent to about 90 percentby weight of fatty acid ester. In the presently preferred products,usually 15 percent to 30 percent of anhydride and 70 percent to percentof oil ester are employed. If an ethylenically unsaturated monomer isincorporated in the reaction product, it is typically used in amountsbetween about 5 percent and about 35 percent by weight based upon thetotal weight of acid or anhydride and ester, with between 10' percentand 25 percent being used in those products preferred. Thus, in mostinstances, the total composition of the reaction product may comprisefrom about 35 percent to about percent by weight of the fatty acid esterand from about 10' percent to about 65 percent of the acid or anhydrideand other monomer combined, with between about 6 percent and about 45percent of the acid or anhydride always present.

The products produced in the above manner are comprised of polymericchains of moderate length. The average molecular weight of the productsto be used in electrodeposition should be low enough so that its flowcharacteristics at high solids are maintained, but high enough toprovide adequate throwing power. The desirable molecular weight levelsvary with the coating composition and conditionsemployed. Generally,those products having molecular weights of up to 10,000 or somewhathigher have given the best results.

The product obtained by reacting the fatty acid ester and thedicarboxylic acid or anhydride and the ethylenically unsaturatedmonomer, if any, is believed to contain recurrent groups derived fromthe dicarboxylic acid or anhydride and which can be represented by thefollowing structure:

The improved compositions of the present invention are obtained byreacting the recurrent groups as described above with a monohydricalcohol, so as to esterify at least some, i.e., at least about 5percent, of the carboxyl groups of the dicarboxylic acid (or thecorresponding anhydride groups). These groups can be reacted with thealcohol either before or after the reaction with the fatty acid esterand any monomers. The preferred compositions, have up to about 50percent of the dicarboxylic acid carboxyl groups esterified, althoughhigher proportions, up to about 80 percent, can be esterified in certaininstances if so desired. The higher levels of esterification are bestemployed when a higher proportion of the dicarboxylic acid or anhydrideis present; the esterified product should if possible have an acid valueof at least about 30 prior to neutralization.

In the preferred compositions, all or part of the foregoing groups ofthe structure II are thus converted to groups which have the followingstructure:

(III) where R is an organic radical derived by elimination of thehydroxyl group from the alcohol employed. The partially esterifiedstructure illustrated is known as the halfester of the dicarboxylic acidgroup.

Essentially any monohydric alcohol can be employed to produce thesehalf-esters, since the products of the invention are achieved with anymonohydric alcohol which, when reacted with the acidic component, formsan ester which is not substantially hydrolyzed in water. The preferredalcohols are alkanols containing up to about carbon atoms, includingmethanol, ethanol, 1- propanol, Z-propanol, l-butanol,Z-methyl-l-propanol (isobutyl alcohol), Z-butanol, and l-pentanol. Alsoquite advantageous are the lower alkyl monoethers of ethylene glycol anddiethylene glycol, such as the monoethyl, monoethyl, monopropyl andmonobutyl ethers of ethylene glycol (Cellosolves), and the correspondingmonoethers of diethylene glycol (Carbitols). Other alcohols which may beutilized are longer chain alcohols, such as linseed fatty alcohol andother fatty alcohols; longer chain monoethers of glycols; cyclicalcohols, such as cyclopentanol, cyclohexanol and furfuryl alcohol; andaromatic alcohols, such as benzyl alcohol. When longer chain alcoholsare employed, it is preferable to utilize relatively high levels of theacid or anhydride, in order to attain good dispersibility in water.

As indicated above, it is preferred that only up to about half of thecarboxyl groups or the anhydride groups derived therefrom are esterifiedby reaction with the alcohol. This is relatively easily accomplishedbecause the half-ester of all of the dicarboxylic acid moieties presentis in most cases preferentially obtained upon reaction with an alcoholbefore the full ester of any of the dicarboxylic acid groups begins tobe formed. In addition, production of the full ester generally requiresmore stringent conditions, such as higher temperatures, even when anexcess of the alcohol is present. Even when only half of the acid groupsare to be esterified, it is not necessary that each dicarboxylic acidform the half-ester. Thus, some of the dicarboxylic acid groups may befully esterified. In actual practice, however, the half-esters of thedicarboxylic acid moieties are usually obtained, due to the preferentialreactivity of the first carboxyl group in each dicarboxylic acid unit.

The esterification of the acidic groups can be carried out at any stageof the process. If desired, the acid or anhydride can be partiallyesterified and the half-ester (or other partial ester) then reacted withthe fatty acid ester and any other monomer. Similarly, the acidiccomponent can be reacted first with the fatty acid ester, thenesterified with the monohydric alcohol, and this product then reactedwith an additional monomer, or the unsaturated mono-mer can be reactedwith the fatty ester and this product reacted with the unesterified orpartially esterified acidic component. Thus, the invention does notreside in any particular mode of carrying out the reactions, and theadvantageous properties of the products do not depend upon the manner ororder in which the various components are coreacted so long as the finalproduct has the composition described.

Generally, however, the esterification reaction with the alcohol iscarried out by admixing the initial reaction product of the ester, theacid or anhydride, and any other monomer with the alcohol. The reactionat room temperature is quite slow, and thus it is preferred to heat thereaction mixture moderately. The preferred maximum temperature is thatat which the full ester begins to be formed,

which varies with the particular alcohol. In most cases, however, thismaximum temperature is about C.

The partially esterified product contains about half of the originalacidity derived from the dicarboxylic acid. It is necessary toneutralize at least part of the remaining acidic groups in order to makethe .product usable in electrodeposition processes, and this isaccomplished by reaction of the partially esterified product with abase. Inorganic bases, such as metal hydroxides or quarternary ammoniumhydroxides, can be used, but it is preferred to employ organic bases,such as amines. Included within the term amines is ammonia, and in manycases ammonia is the preferred neutralizing base. Also quite effectiveis any basic primary or secondary amine. These include, for example,alkyl amines such as methylamine, ethylamine, propylamine, butylamine,amylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine andN-methylbutylamine; cycloalkyl amines, such as cyclohexylamine;unsaturated amines, such as allyl amine, 1,Z-dimethylpentenylamine andpyrrole; arylamines, such as aniline; aralkylamines, such as benzylamineand phenethylamine; alkarylamines, such as m-toluidine; cyclic amines,such as morpholine, pyrrolidine and piperidine; diamines, such ashydrazine, methylhydrazine, 2,3-toluenediamine, ethylenediamine,1,2-naphthylene diamine and piperazine; and substituted amines, such ashistamine, hydroxylamine, ethanolamine and diethanolamine. It has beenfound advantageous in many instances to effect part of theneutralization with a diamine and part with ammonia or one of the otherforegoing amines. In other cases, improved properties may be obtained byeffecting part of the neutralization with amines such as theaminoalkyl-alkanediols, for example, 2methyl-2-amino-l,3- propanediol,2-ethyl-2-amino-1,3-propanediol, or Z-methyl-Z-amino-1,4-butanediol.

All or part of the remaining acidity of the product after the partialesterification is carried out can be neutralized. The extent ofneutralization depends to some degree upon the proportion of acidicgroups that have been esterified; the higher the level ofesterification, the larger the proportion of the remaining acidity whichshould be neutralized. Generally, at least about 10 percent of theremaining acidity should be neutralized, and preferably at least about25 percent is neutralized. The neutralization reaction is accomplishedby mixing the neutralizing base with the partially esterified product. Awater solution or other solution of the base may be used if desired, andmoderately elevated temperatures are often employed.

When used in electrodeposition processes, the foregoing products can beemployed as such to electrodeposit clear films, but ordinarily they areused as a vehicle along with a pigment composition and the coatingcomposition is dispersed in water. The pigment composition used may beof any conventional type, comprising, for example, iron oxides, leadoxides, strontium chromate, carbon black, titanium dioxide, talc, bariumsulfate and the like, as well as combinations of these and similarpigments. Usually, it is preferred that an inhibitive pigment, such asstrontium chromate, be included. Color pigments, such as cadmium yellow,cadmium red, phthalocyanine blue, chromic yellow, toluidine red,hydrated iron oxide and the like, may be included if desired, as may bedispersing or surface-active agents. If a surface-active agent is used,it should be of a non-ionic or anionic type, or a combination of thesetypes, since it is desirable to avoid the use of a cationic typesurface-active agent.

Usually the pigment and the surface-active agent, if any, are groundtogether in a portion of the vehicle to make a paste, and this isblended with the vehicle to produce the coating composition. There mayalso be included in the coating composition additives, such asanti-oxidants, wetting agents, driers, anti-foaming agents,bactericides, suspending agents and thelike.

It has been found that in most instances desirable coatings are obtainedusing pigmented compositions containing ratios of pigment-to-vehicle ofnot higher than about 1.5 to l, and preferably not higher than about 1to 1. If the composition has too high a pigment-to-vehicle ratio, theelectrodeposited film may exhibit poor flow characteristics, and in manyinstances is noncontinuous and therefore subject to deterioration.

In formulating the coating composition, ordinary tap water may beemployed. However, such water may contain a relatively high level ofcations which, while not ordinarily rendering the process inoperative,may result in variations in the properties of the bath when used forelectrodeposition. Thus, it is often desirable to utilize deionizedwater from which free ions have been removed, as by passage through anion exchange resin, in making up the coating compositions of theinvention, especially when the composition is intended for use in anelectrodeposition process.

The compositions as described above can be applied in any conventionalmanner, but they are especially adapted to electrodeposition. Inelectrodeposition processes utitrically conductive metal anode and anelectrically containing the composition is placed in contact with anelectrically conductive metal anode and an electrically conductivecathode. The coating is deposited upon the anode, so that the metalsubstrate to be coated is used as the anode. It may be of anyelectrically conductive metal, such as iron, steel, aluminum, galvanizedsteel, phosphatized steel, zinc and the like. Upon the passage ofelectric current between the anode and the cathode, While in contactwith the bath containing the coating composition, an adherent film ofthe coating composition is deposited upon the anode.

The conditions under which the electrodeposition process is carried outcan 'be those conventionally used in the electrodeposition methodsemployed heretofore. The applied voltage may be varied greatly, and canbe very low, e.g., 1 volt, or very high, e.g., 500 volts or even higher.It is typically between 50 volts and 350 volts. The current densitydepends on the area of the anode; the initial current density is usuallybetween about 0.1 ampere per square foot and amperes per square foot.The current generally decreases somewhat during electrodeposition.

It is desirable that the pH of the coating composition be as low asposisble, consistent with the desired level of neutralization, andpreferably under about 8.0. There is a correlation between the extent ofneutralization and the pH of the neutralized product, so thatmeasurement of pH provides a convenient method of determining theapproximate extent to which neutralization has taken place. However, thepH for any given level of neutralization varies with the nature of thecomponents of the coating composition, that is, with the particularvehicle and pigment composition included therein. The nature of thealcohol used to effect the partial esterification also affects the pH;the longer the chain length of the alcohol employed, the higher the pHdesired. The presence of an additional unsaturated monomer alsoincreases the preferred pH level.

In some instances, either due to an inadvertent addition of excessneutralizing base, or to the particular characteristics of the reactionsystem involved, the resulting product has a pH above the desired level.When this occurs, it has been found that the pH may be convenientlylowered by the addition of an additional quantity of the partiallyesterified product that is unneutralized, or only slightly neutralized,i.e., products of the above type in which about percent or less of theremaining acidity has been neutralized. The addition of theunneutralized or slightly neutralized resin not only effectively reducesthe pH to a desired level, but unexpectedly does not deleteriouslyaffect the stability or other properties of the coating com positionwhen used in electrodeposition processes.

The problem of increased pH is especially encountered in. continuouselectrodeposition of the coating compositions of the invention. Thus,there is a tendency to build up a concentration of cations in theelectrodeposition bath, and this is manifested by an increase in the pHof the bath. When this occurs, there is a subsequent deterioration inthe quality of the deposited film. In addition to film degradation, thebuildup in cations leads to a bath having higher conductivity, which inturn requires higher current densities to deposit films of a suitablethickness. This may be overcome by the addition of unneutralized or onlyslightly neutralized product to baths employed in continuouselectrodeposition which lowers the pH of the bath without affecting theadvantageous properties of the composition.

The concentration of the coating composition in the aqueous bath used inelectrodeposition is not critical and relatively high levels of thecoating composition can be used. However, it is ordinarily desirable touse as low a concentration of a coating composition as will givesatisfactory results, and it is in this respect that the coatingcompositions of this invention are particularly advantageous. Bathscontaining as little as about 1 percent by weight of the coatingcomposition in water can be employed, and in ordinary practice, thebaths utilized usually contain between about 5 percent and about 10percent by weight. Generally, it is preferred not to use more than about20 percent by weight of the coating composition in the bath.

Electrodeposition produces an adherent film which is very high in solidscontent, often percent to percent or even higher, which provides theimportant advantage that the film will not readily run or wash. Thearticle so coated can be used, if desired, without additional baking orother drying procedures; if it is desired to carry out an additonalbaking or drying of the film, this is easily accomplished inasmuch asthere is little or no solvent to be evaporated from the film. When thisis done, baking temperatures of about C. to 200 C. for about 10 minutesto 30 minutes are usually used.

The optimum voltages and current densities used may vary depending uponthe coating composition used and the particular characteristics desiredin the finished coating. Thus, it has been found that thicker films aregenerally obtained with higher voltages, and that greater throwing powerresults from use of higher voltages for given film thickness. Usually amaximum film thickness can be obtained with any given composition, andthis depends upon the conductivity of the bath containing thecomposition, which in turn depends largely upon the extent ofneutralization. However, any of the compositions described above willproduce satisfactory coatings having suflicient adherency and thicknessusing the ordinary methods and conditions heretofore used inelectrodeposition processes.

Below are several specific examples of the invention.

Examples 1 to 5 demonstrate the manner in which the vehicles areproduced and incorporated into coating compositions; Examples 6 to 12illustrate the electrodeposition of films of such compositions. Theseexamples, however, are not to be construed as limiting the invention totheir details.

Example 1 A 5-liter reactor was charged with 2280 parts of linseed oiland 720 parts of maleic anhydride, heated to 220 C. and held at thattemperature for about 3 hours. It was then sparged with an inert gas for10 minutes and cooled. Partial esterification of the product was carriedout by adding 233.5 parts of methanol slowly to 2500 parts of theforegoing product at 80 C. After 2 /2 hours, during which thetemperature was raised to 95 C., the mixture was sparged with inert gasfor '10 minutes and cooled. Neutralization was then carried out bymixing 1500 parts of partially esterified product with 80 parts of a 28percent solution of ammonia in water and 2100 parts of deionized water.The product had a pH of 6.85 and a nonvolatile solids content of 39.8percent.

A pigment composition was made by grinding the following for 16 hours ina steel ball mill to form a paste.

Parts by weight Vehicle made above (39.8 percent solids) 118.5 Deionizedwater 220 Dispersing agent (Witco 912, a combination oilsolublesulfonate and nonionic surfactant) 5.6 Red iron oxide 513.9 Carbon black28.0 Strontium chromate 19.1

To this pigment paste there were added 188.5 parts of the vehiclesolution above, whereupon the pigment composition produced was comprisedof 9.44 percent vehicle solids and 54.51 percent pigment solids.

A water-dispersed coating composition was prepared from the abovevehicle and pigment composition by mixing 407 parts of the vehiclesolution with 197 parts of the pigment composition and 2996- parts ofdeionized water, with the addition of 1.8 parts of cresol as ananti-oxidant.

Example 2 A reaction product of maleic anhydride and linseed oil wasmade and partially esterfied as in Example 1. This product wasneutralized by mixing 150 parts of the partially esterified adduct with8 parts of a 28 percent solution of ammonia in water and 210 parts ofdeionized water. A clear, unpigmented, water-dispersed coatingcomposition was then produced from this vehicle by mixing it with 2632parts of deionized water.

Example 3 A -liter reaction vessel was charged with 2400 parts oflinseed oil and 600 parts of maleic anhydride. This mixture was heatedto 220 C. and maintained at that temperature for 1 /2 to 3 hours oruntil the viscosity was about 20,000 centipoises at 25 C. It was thensparged with inert gas for 15 minutes and cooled to 150 C. There werethen added 1.5 parts of ditertiary butyl peroxide and, while maintainingthe reaction mixture at 150 C. to 155 C., a mixture of 750 parts ofstyrene and 7.5 parts of ditert'iary butyl peroxide was slowly anduniformly added over a period of 4 hours. When the addition wascomplete, 3.75 parts of ditertiary butyl peroxide were added and themixture was heated at 160 C. for 1 hour. The temperature was raisedgradually to 200 C. and maintained for /2 hour. The mixture was thensparged with inert gas for /2 hour and cooled.

Esterification of the foregoing product was carried out by mixing 2500parts of the above product with 135 parts of methanol. This mixture wasstirred and heated slowly to 90 C. over a period of 1% hours, andmaintained at 90 C. to 95 C. for an additional 1%. hours. It was thensparged with an inert gas for 20 minutes and cooled. The product thusobtained was neutralized by mixing and stirring 150 parts thereof with210 parts of deionized water and 7 parts of 28 percent ammonia in water.The vehicle thus produced had a solids content of 40.8 percent.

A coating composition was then produced from the foregoing vehicle and apigment composition comprised of 90 percent red iron oxide, 5 percentstrontium chromate and 5 percent carbon black as the pigment solids,along with a dispersing agent which was ground in the foregoing vehicle.The ratio of pigment solids to vehicle solids of the coating compositionproduced was 0.4 to 1, and sufficient deionized water was added to makethe total solids content of'the resultant water-dispersed composition 7percent.

Example 4 A reaction product of maleic anhydride, linseed oil andstyrene was produced as in Example 3. The ethyl half-ester of thisproduct was then produced by mixing 3000 parts of the reaction productwith 258 parts of ethanol and heating this mixture to C. After 1 hour atthis temperature, the mixture was sparged with an inert gas for 15minutes and cooled. The esterified product was then neutralized byadding 2500 parts thereof to a solution of 83 parts of 28 percentammonium hydroxide and 3000 parts of deionized water. After stirring,there were added an additional 1500 parts of deionized water andsufficient ammonium hydroxide to make the pH 7.25, and the resultantproduct filtered. The vehicle thus produced had a solids content of 34.5percent.

A pigment composition was produced by adjusting the pH of 202.4 parts ofthe foregoing vehicle to 9.0 with ammonium hydroxide and then adding 4parts of a dispersing agent (Witco 912), 390 parts of red iron oxide and10 parts of strontium chromate. This mixture was ground in a steel ballmill for 16 hours and then 99.2 parts of the vehicle were added and thismixture was ground for an additional 30 minutes. The resulting pigmentpaste was comprised of 13.3 percent vehicle solids and 56.7 percentpigment solids.

A Water-dispersed coating composition was produced from the foregoingvehicle and pigment paste by mixing 158.4 parts of the foregoing pigmentpaste with 645.1 parts of the vehicle and 2409 parts of deionized water,along with 3.83 parts of an anti-oxidant. The total solids content ofthe composition was 10 percent.

Example 5 A reaction product made as in Example 3 from maleic anhydride,linseed oil and styrene was esterified by reacting 3291 parts of theresinous material with 407 parts of isobutanol at C. for 1 hour. Aftersparging this with an inert gas for 20 minutes, 3000 parts of theproduct obtained were mixed with 3600 parts of deionized Water and 100parts of 28 percent ammonium hydroxide. This product was then mixed withsufiicient deionized water to make the total solids content 5 percent,whereby there was produced a clear, unpigmented coating composition.

The foregoing examples illustrate the method of producing vehicles andcoating compositions in accordance with the invention. The followingexamples demonstrate the method and practice of carrying out theelectrodeposition of the coating compositions described above, andillustrate the nature and advantages of the results obtained therefrom.

Examples 6 to 12 In carrying out each of these examples, the coatingcomposition employed was placed in a magnetically stirred, l-gallonpolyethylene container. The electrodes used were 4-inch by 12-inchphosphatized steel (Bonderite) panels, and an electromotive force wasapplied between the electrodes from a 0 to 1000-volt industrialrectifier (Dresser Electric). The electrodes were spaced 2 inches apartin the bath and were immersed in the coating composition to a depth of 6inches. The throwing power of a particular coating composition wasdetermined by first carrying out an electrodeposition using a singlepanel as the cathode and another single panel as the anode, usingsufficient voltage and time to give a film of 1 mil thickness on theanode. The single anode panel was then replaced with three panels joinedat the bottom and separated at the top by shims 4 inches by 4 inches,beveled from inch in thickness at the top to inch at the bottom. Theelectrodeposition was then repeated with the conditions which gave a 1mil thick coating. The throwing power of the bath is defined as thatpercentage of the immersed portion of the center panel of the anode uponwhich an adherent film had been deposited. The coatings were then driedby baking and the properties of thedeposited film determined usingstandard procedures. Table I below sets forth the data obtained from thevarious tests carried out in the above manner.

TAB LE I Coating Concentrav I Composition Pigment tion in Water Bath,Applied Current Bath Deposition Throwing Baking Baking Film Ex. No. asin to Vehicle (percent pH EMF (amp) Temp. Time Power Temp. Time HardnessExample Ratio solids) (volts) F.) (sec.) (percent) F.) (111111.)(pencil) 1 8 6. 6 150 2. 1-1. 35 96 90 90-95 350 20 B 2 i 6. 7 110 l. 40. 6 88 90 350 613+ 2 5 6. 7 110 1. 40. 6 88 120 350 20 613+ 3 0. 4/1 77.8 220 2. 2-1. 90 60 85-90 350 20 13-1113 3 0. 4/1 7 7. 8 190 1. 9-1. 192 90 90-95 350 20 B 4 0. 4/1 10 7. 3 170 3. 31. 9 86 90 95 350 20 5B 55 7. 5 220 2. 0-1. 1 74 90 350 20 B-3B while especially efficacious forelectrodeposition, can also be used to produce coatings havingadvantageous properties utilizing more conventional applicationtechniques. For example, the coating composition of Example 2, whendrawn on a phosphatized steel panel with a 3-mi1 drawdown bar and thenair dried for /2 hour and baked at 350 F. for minutes, produced a hard,adherent film of excellent properties. The film was about 1 mil thickand had a 4B pencil hardness. Similar results are attained by applyingcoatings by brushing, spraying or dipping, and then baking.

According to the provisions of the patent statutes, there are describedabove the principle of the invention and what are now considered to beits best embodiments. However, within the scope of the appended claims,it is to be understood that the invention can be practiced otherwisethan is specifically described.

We claim:

1. In a method of coating a metal substrate which comprises passing anelectric current between an electrically conductive metal anode and anelectrically conductive cathode in contact with an aqueous bathcomprising a partially esterified and partially neutralized product of afatty acid ester and an acidic compound, the additional step of addingto said bath a composition comprising a vehicle which comprises areaction product of an ester selected from the class consisting ofdrying oil fatty acid esters and semi-drying oil fatty acid esters withat least one acidic compound selected from the group consisting ofanhydrides of alpha, beta-ethylenically unsaturated dicarboxylic acids,alpha, beta-ethylenically unsaturated dicarboxylic acids which formanhydrides, said reaction product having up to about half of the acidiccarboxyl groups esterified by reaction with a water-soluble monohydricalcohol and up to about 20 percent of the unesterified acidic carboxylgroups neutralized.

2. The step as in claim 1 in which the composition is added in amountssufficient to maintain the pH of the water-dispersed coating compositionbetween about 6.0 and about 7.5.

3. A method of coating a metal substrate which comprises passingelectric current between an electrically conductive metal anode and anelectrically conductive cathode in contact with an aqueous-coatingcomposition containing a dissolved vehicle consisting essentially of thereaction product of an ester selected from the class consisting ofdrying oil fatty acid esters and semi-drying oil fatty acid esters withat least one acidic compound se lected from the group consisting ofanhydrides of alpha, beta-ethylenically unsaturated dicarboxylic acids,alpha, beta-ethylenically unsaturated dicarboxylic acids which formsanhydrides, furnaric acid, and mixtures thereof, at least some of theacidic carboxyl groups of said acidic components having been esterifiedby reaction with a monohydric alcohol and at least about 10 percent ofthe unesterified acid carboxyl groups having been neutralized.

indicated above, the compositions of the invention,

4. The method of claim 3 in which said reaction product contains betweenabout 55 percent and about 90 percent by weight of said ester andbetween about 10 percent and about percent by weight of said acidiccompound and up to about percent of the acidic carboxyl groups areesterified.

5. A method of coating a metal substrate which comprises passing anelectric current between an electrically conductive metal anode and anelectrically conductive cathode in contact with an aqueous coatingcomposition containing a dissolved vehicle consisting essentially of areaction product of an ester selected from the class consisting ofdrying oil fatty acid esters and semi-drying oil fatty acid esters with(a) at least one acidic compound selected from the group consisting ofanhydrides of alpha, beta-ethylenically unsaturated dicarboxylic acids,alpha, betaethylenically unsaturated dicarboxylic acids, which formanhydrides, fumaric acid, and mixtures thereof, and

(b) at least one ethylenically unsaturated monomer; at

least some of the acidic carboxyl groups of said acidic compound havingbeen esterified by reaction with a monohydric alcohol and at least about10 percent of the unesterified acidic carboxyl groups having beenneutralized.

6. The method of claim 5 in which said reaction product contains betweenabout 35 percent and about 90 percent by weight of said ester, fromabout percent to about 45 percent by weight of said acidic compound, andfrom about 5 percent to about 35 percent by weight of said ethylenicallyunsaturated monomer, and up to about 50 percent of the acidic carboxylgroups are esterified.

7. The method of claim 5 in which the coating composition contains waterin an amount between about percent and about 99 percent of the totalweight thereof, and contains pigment in a weight ratio of pigment tovehicle no greaer than about 1.5 to 1.

8. The method of claim 3 in which said coating composition containswater in an amount between about 80 percent and about 99 percent of thetotal weight thereof, and contains pigment in a weight ratio of pigmentto vehicle not greater than about 1.5 to 1.

, References Cited UNITED ROBERT K. MIHALEK, Primary Examiner. JOHN H.MACK, Examiner.

E. ZAGARELLA, Assistant Examiner.

1. IN A METHOD OF COATING A METAL SUBSTRATE WHICH COMPRISES PASSING ANELECTRIC CURRENT BETWEEN AN ELECTRICALLY CONDUCTIVE METAL ANODE AND ANELECTRICALLY CONDUCTIVE CATHODE IN CONTACT WITH AN AQUEOUS BATHCOMPRISING A PARTIALLY ESTERIFIED AND PARTIALLY NEUTRALIZED PRODUCT OF AFATTY ACID ESTER AND AN ACIDIC COMPOUND, THE ADDITIONAL STEP OF ADDINGTO SAID BATH A COMPOSITION COMPRISING A VEHICLE WHICH COMPRISES AREACTION PRODUCT OF AN ESTER SELECTED FROM THE CLASS CONSISTING OFDRYING OIL FATTY ACID ESTERS AND SEMI-DRYING OIL FATTY ACID ESTERS WITHAT LEAST ONE ACIDIC COMPOUND SELECTED FROM THE GROUP CONSISTING OFANHYDRIDES OF ALPHA, BETA-ETHYLENICALLY UNSATURATED DICARBOXYLIC ACIDS,ALPHA, BETA-ETHYLENICALLY UNSATURATED DICARBOXYLIC ACIDS WHICH FROMANHYDRIDES, SAID REACTION PRODUCT HAVING UP TO ABOUT HALF OF THE ACIDICCARBOXYL GROUPS ESTERIFIED BY REACTION WITH A WATER-SOLUBLE MONOHYDRICALCOHOL AND UP TO ABOUT 20 PERCENT OF THE UNESTERIFIED ACIDIC CARBOXYLGROUPS NEUTRALIZED.